I. Field of the Invention
This invention relates generally to wireless communication systems and more particularly to beamforming in a millimeter-wave wireless communication system.
II. Description of the Related Art
In one aspect of the related art, a dual-mode ultra-wideband (UWB) Physical Layer supporting single carrier and OFDM modulation employs a common mode. The UWB Physical Layer may be used for millimeter wave (e.g., 60 GHz) communications. The common mode is a single-carrier mode used by both single-carrier and OFDM devices for beaconing, network-control signaling, and base-rate data communications. The common mode is typically necessary for interoperability between different devices and different networks.
Millimeter-wave communications may also employ MIMO (multiple input multiple output) beamforming to provide both spatial diversity and array gains. Conventional beamforming, such as Eigen-beamforming, requires channel state information matrices or beamforming matrices to be returned to the transmitting array. The IEEE 802.11n MAC/PHY Specifications D0.04, March 2006, specifies feedback information that includes row and column sizes of the feedback matrices, subcarrier grouping size (or cluster size), quantization bit size, and an array of actual quantized data elements starting in the order of the lowest subcarrier index to the highest subcarrier index. For beamforming that employs precoding matrices, the feedback information can be reduced by replacing beamforming matrix contents with indices of a precoding-matrix codebook, such as described in the IEEE 802.16e MAC/PHY Specifications D12, 2005, and in D. J. Love, R. W. Heath Jr., and T. Strohmer, “Grassmannian Beamforming for Multiple-Input Multiple-Output Wireless Systems”, IEEE Trans. Information Theory, Vol. 49, No. 10, October 2003, pp. 2735-2747).